MPTP对快速老化小鼠黑质纹状体系统的急性损害及小胶质细胞的激活

目的:探讨MPTP(1-甲基-4-苯基-1,2,3,6-四氢吡啶)对快速老化小鼠(senescence accelerated mouse prone8,SAMP-8)黑质纹状体系统的急性损害及小胶质细胞激活与损害的关系。方法:57只健康雄性12周龄SAMP8小鼠,随机分为生理盐水对照组和MPTP组,每组再分别于第1次给药后6 h、24 h、3 d和8 d四个时间点处死小鼠,每个时间点6~9只。SAMP8小鼠背部皮下注射MPTP 20 mg·kg-1,1次/2 h,注射4次,观察各时间点小鼠的自主活动;免疫组织化学染色检测各时间点黑质TH+神经元数量、纹状体TH免疫反应性及小胶质细胞的状态;HPLC技术检测纹状体DA含量。结果:第3次注射后小鼠出现明显活动减少,并于第1次给药后48 h恢复近正常水平。与对照组相比:MPTP组黑质TH+神经元数目于第1次注射后6 h、24 h、3 d、8 d分别减少7.06%(P=0.235)、12.79%(P<0.05)、22.49%(P<0.01)、42.39%(P<0.001),两个时间点之间比较3 d与8 d有统计学差异(P<0.05);与对照组相比,MPTP组纹状体TH免疫反应性(COD值)减低,6 h (P<0.05)、24 h (P<0.01)、3 d (P<0.001)、8 d (P<0.001),两个时间点之间比较24 h与3 d比较差异有统计学意义(P<0.05);纹状体多巴胺含量6 h降低79.09% (P<0.001),24 h降低80.3% (P<0.001),3 d降低86.6% (P<0.001),8 d降低81.0% (P<0.001),但24 h、3 d、8 d比较无统计学差异。纹状体小胶质细胞于给药后24 h免疫反应性明显增强,3 d明显激活,8 d激活现象明显回落。结论:MPTP可导致SAMP8小鼠黑质纹状体系统的急性损害,出现自主活动减少、黑质多巴胺能神经元减少及纹状体多巴胺能纤维脱失,多巴胺含量降低;小胶质细胞激活可能与MPTP-SAMP8小鼠的黑质纹状体系统损伤有关。

Acute damage of nigrostriatal system in MPTP-treated senescence accelerated mouse and damage-related microglial activation

Objective:To investigate the acute damage of the nigrastriatal system in SAMP8 mouse after treatment with MPTP and its relationship with microglial activation.Methods: Totally 57 male SAMP8 mice were randomly divided into two groups,control group and MPTP group.Mice were sacrificed (each time 6-9 mice) at 6 h,24 h,3 d,and 8 d after the first injection in each group.Mice were subcutaneously injected with normal saline or MPTP (20 mg/kg) at an interval of 2 h for 4 times.The changes of spontaneous activity of mice were observed after injection.The changes of TH+ (tyrosine hydroxylase positive) neuronal numbers in the substantial nigra,TH-ir (tyrosine hydroxylase immunoreactivity), and microglial activation in striatum were examined by immunohistochemistry; striatal dopamine (DA) levels were determined by HPLC.Results: The spontaneous activity of SAMP8 mice was decreased significantly after the third injection,and recovered at 48 h after the first injection. Compared with the control group,the TH+ neurons in MPTP group decreased by 7.06% at 6 hours (P=0.235),by 12.79% at 24 hours(P<0.05),by 22.49% at 3 days(P<0.01),and by 42.39% at 8 days(P<0.001); there was significant difference in the TH+ neurons between the 3 days and 8 days (P<0.05).The corrected optical densities (COD) of TH-ir in the striatum in MPTP group were significantly lower than those in the control group at different time points (6 h,[P<0.05],24 h[P<0.01],3 d[P<0.001],8 d[P<0.001]); there was significant difference between the 24 h and 3 days groups (P<0.05).Compared with the control group,the striatal dopamine (DA) levels decreased by 79.09% at 6 hours ( P<0.001),by 80.3% at 24 hours (P<0.001),by 86.6% at 3 days (P<0.001),and by 81.0% at 8 days (P<0.001); there were no significant difference between the 24 h,3 days,and 8 days.The immunoreactivity of microglial greatly increased at 24 hours,further activated at 3 days,and largely abated at 8 days after MPTP injection.Conclusion: MPTP can cause acute damage to substantia nigra of SAMP8 mice,resulting in reduced spontaneous activity and dopaminergic neurons loss; the activation of microglial might be related to the nigrostriatum damage of MPTP-SAMP8 mice.